C-band orthomode transducer for compact and broadband antenna feeders

The design and evaluation of a compact C-band orthomode transducer for dual polarisation satellite communications is presented, covering the bands 3.7-4.2 GHz and 5.925-6.425 GHz (54% of fractional bandwidth separation). Over such a broadband, the main difficulty is to obtain a compact structure able to fulfil the stringent satellite specifications with minimum longitudinal length. The proposed configuration, validated with a tested prototype, also reduces the number of connections and parts in the fabrication, decreasing the passive intermodulation risk and the mass and volume.     

Synthesis and design of waveguide band-stop filters without out-of-band spurious responses for plasma diagnosis

Band-stop or notch filters play a crucial role in plasma diagnosis systems to protect receivers from the stray radiation. In this work, a rigorous design process based on circuit synthesis in addition to an extremely compact E-plane waveguide structure is proposed for this kind of filters. On the one hand, the transfer function verifying the rejection specification is analytically obtained, fixing the minimum number of required cavities. On the other hand, a coupling structure that reduces drastically the unwanted resonances in filters with a very large pass band requirement, is presented. This coupling between the rejection cavities and the main rectangular waveguide has additional advantages; (a) unlike typical inductive irises, large coupling coefficients can be implemented (b) a pure E-plane configuration is achieved, which simplifies the manufacturing and also reduces significantly the computational effort. Experimental validation is demonstrated by two pseudo-elliptic fifth-order band-stop filters fabricated and measured in Ka and V bands. In both cases, the filters are free of spurious resonances in their total operation bands.     

Full-wave design and realization of multicoupled dual-mode circularwaveguide filters

A new full-wave method for the design and realization of dual-mode circular waveguide filters is presented. The rigorous CAD is a combination of the mode-matching and the finite-element techniques, which permits obtaining the Generalized Scattering Matrix for all the blocks that compose the structure (rectangular slots, cross-irises, and screws). The finite thickness of the irises, the higher order mode interaction, as well as the coupling and tuning screws are rigorously taken into account. A systematic design process for the different elements is described. A full prediction of resonant out-of-band spurious modes is accomplished prior to the filter construction. Special attention is devoted to the circuital model in order to save a great deal of computational effort in the final adjustment. A four-pole elliptic circular waveguide cavity filter has been designed and constructed. The experimental filter results show excellent agreement with theory     

Amplified Recirculating Delay Lines as Fiber-optic Decoders in TV Systems

A novel approach to decoding chrominance signal in amplitude-modulated vestigial-sideband (AM-VSB) television systems is described. The decoding scheme is achieved by means of amplified recirculating delay lines as fiber-optic filters. The technique is experimentally verified by decoding the chrominance components of the UHF channel 21 of G PAL standard.     

Synthesis of N-order filters with N transmission zeros at real frequencies by means of extracted poles

The synthesis of N-order filters with N transmission zeros at real frequencies by means of extracted poles is presented. A procedure to extract the circuit elements that implement the finite insertion losses for infinite frequency is explained. To verify this procedure, three different implementations of a fourth-order filter with four transmission zeros are presented.     

Synthesis and design of in-line N-order filters with N real transmission zeros by means of extracted poles implemented in low-cost rectangular H-plane waveguide

In this paper, an extension to the extracted pole technique for synthesizing N-order filters with N-transmission zeros at real frequencies is presented. In addition, a new bandpass rectangular waveguide H-plane low-cost configuration filter for high-power low-loss application (patent pending) that implements a filtering function with finite real frequency transmission zeros is proposed. This structure operates as a resonant cavity in transmission at central frequency of the bandpass and simultaneously introduces a controlled transmission zero out of the bandpass. Since every double-controlled electrical behavior cavity introduces a transmission zero, it is possible to introduce as many transmission zeros as the order of the filtering function. In order to validate the synthesis procedure and the new structure, different filters have been designed: a second-order filter with two transmission zeros, a third-order filter with one transmission zero, a fourth-order filter with two transmission zeros, and finally, an eighth-order filter with two transmission zeros. The last two have been manufactured, showing an excellent agreement between the measurement and theoretical simulation.     

Synthesis of filters with transmission zeros at real frequencies bymeans of trisections including source/load to resonator coupling

Filter synthesis based on trisections is extended to the case where coupling is between the source/load (input/output ports) and the resonators. Using this coupling, two transmission zeros can be placed at different real frequencies (jw axis of the complex plane) and independently controlled. For odd order filters: a new network transformation between the ladder network and the equivalent trisection is proposed. To validate the above transformation, a fifth degree two-trisection filter has been synthesised